text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2020 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  #include "stdlib/stats/base/dvariancewd.h"
  #include <node_api.h>
  #include <stdint.h>
  #include <stdbool.h>
  #include <assert.h>
  
  /**
  * Add-on namespace.
  */
  namespace stdlib_stats_base_dvariancewd {
  
  	/**
  	* Computes the variance of a double-precision floating-point strided array using Welford's algorithm.
  	*
  	* ## Notes
  	*
  	* -   When called from JavaScript, the function expects four arguments:
  	*
  	*     -   `N`: number of indexed elements
  	*     -   `correction`: degrees of freedom adjustment
  	*     -   `X`: input array
  	*     -   `stride`: stride length
  	*/
  	napi_value node_dvariancewd( napi_env env, napi_callback_info info ) {
  		napi_status status;
  
  		size_t argc = 4;
  		napi_value argv[ 4 ];
  		status = napi_get_cb_info( env, info, &argc, argv, nullptr, nullptr );
  		assert( status == napi_ok );
  
  		if ( argc < 4 ) {
  			napi_throw_error( env, nullptr, "invalid invocation. Must provide 4 arguments." );
  			return nullptr;
  		}
  
  		napi_valuetype vtype0;
  		status = napi_typeof( env, argv[ 0 ], &vtype0 );
  		assert( status == napi_ok );
  		if ( vtype0 != napi_number ) {
  			napi_throw_type_error( env, nullptr, "invalid argument. First argument must be a number." );
  			return nullptr;
  		}
  
  		napi_valuetype vtype1;
  		status = napi_typeof( env, argv[ 1 ], &vtype1 );
  		assert( status == napi_ok );
  		if ( vtype1 != napi_number ) {
  			napi_throw_type_error( env, nullptr, "invalid argument. Second argument must be a number." );
  			return nullptr;
  		}
  
  		bool res;
  		status = napi_is_typedarray( env, argv[ 2 ], &res );
  		assert( status == napi_ok );
  		if ( res == false ) {
  			napi_throw_type_error( env, nullptr, "invalid argument. Third argument must be a Float64Array." );
  			return nullptr;
  		}
  
  		napi_valuetype vtype3;
  		status = napi_typeof( env, argv[ 3 ], &vtype3 );
  		assert( status == napi_ok );
  		if ( vtype3 != napi_number ) {
  			napi_throw_type_error( env, nullptr, "invalid argument. Fourth argument must be a number." );
  			return nullptr;
  		}
  
  		int64_t N;
  		status = napi_get_value_int64( env, argv[ 0 ], &N );
  		assert( status == napi_ok );
  
  		double correction;
  		status = napi_get_value_double( env, argv[ 1 ], &correction );
  		assert( status == napi_ok );
  
  		int64_t stride;
  		status = napi_get_value_int64( env, argv[ 3 ], &stride );
  		assert( status == napi_ok );
  
  		napi_typedarray_type vtype2;
  		size_t xlen;
  		void *X;
  		status = napi_get_typedarray_info( env, argv[ 2 ], &vtype2, &xlen, &X, nullptr, nullptr );
  		assert( status == napi_ok );
  		if ( vtype2 != napi_float64_array ) {
  			napi_throw_type_error( env, nullptr, "invalid argument. Third argument must be a Float64Array." );
  			return nullptr;
  		}
  		if ( (N-1)*llabs(stride) > (int64_t)xlen ) {
  			napi_throw_range_error( env, nullptr, "invalid argument. Third argument has insufficient elements based on the associated stride and the number of indexed elements." );
  			return nullptr;
  		}
  
  		napi_value v;
  		status = napi_create_double( env, stdlib_strided_dvariancewd( N, correction, (double *)X, stride ), &v );
  		assert( status == napi_ok );
  
  		return v;
  	}
  
  	napi_value Init( napi_env env, napi_value exports ) {
  		napi_status status;
  		napi_value fcn;
  		status = napi_create_function( env, "exports", NAPI_AUTO_LENGTH, node_dvariancewd, NULL, &fcn );
  		assert( status == napi_ok );
  		return fcn;
  	}
  
  	NAPI_MODULE( NODE_GYP_MODULE_NAME, Init )
  } // end namespace stdlib_stats_base_dvariancewd
  